1. Field of the Invention
The invention relates to a method of transforming a stored symbol into an "italic" symbol having improved print quality. More specifically, the invention relates to a method for slanting a generic symbol and automatically inserting corrective pixels in a predetermined transformation of the generic symbol without expending memory space for storage of the corrective pixels.
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2. Description of Related Art
It is desirable to manufacture a printer which provides high quality text and graphics and moderate speed at a low cost. One factor increasing the cost of printers is the expense of storing many bits of font data, especially at resolutions needed for quality printing. Accordingly, a printer could be provided with sufficient font storage for storing a font in several different forms such as generic, italic or bold form to provide quality printing, but such a printer would be relatively expensive due to increased font storage needs. If sufficient processing power is available, the font storage needs can be reduced by storing one font in its generic form and altering it in as many ways as needed. Such alterations are usually restricted to slight modifications, such as bolding, compressing and expanding.
To "italicize" a font, it is possible to alter the generic font format (FIG. 1A) by sloping the vertical pixels and leaving the horizontal pixels displaced but still horizontal. Typically, the slope is a horizontal displacement (or rightward displacement in FIG. 1A) of one pixel for a vertical rise of four pixels (FIG. 1B). This slope, however, leads to a staircase edge which reduces print quality at 300 spots per inch (spi). A font designer would partially hide the steps of the staircase edge by tediously adding pixels (such as "a", "b" and "c" in FIG. 1C) near the steps, but this insertion of step concealing pixels increases font storage and decreases printer speed due to relatively complex pixel placement programming requiring time consuming decisional steps to determine where to insert the step-concealing pixels. This counteracts any advantages obtained by a decrease in font storage and an increase in print quality due to the use of the font transformation. It is believed that the Hewlett-Packard Desk-Jet Plus has italic capability by font transformation but does not add the additional step concealing pixels.
It is thus an object of the invention to provide a method of "italicizing" a font which obviates the foregoing disadvantages.
It is a further object of the invention to provide a method for "italicizing" a font using a font transformation that automatically inserts step-concealing pixels in a predetermined transformation without substantially increasing font storage or decreasing printer speed.
It is another object of the invention to provide a method for "italicizing" a font by inserting step concealing pixels without storing the step-concealing pixels.
These and other objects and advantages are obtained by the inventive method for "italicizing" a font which includes the steps of slanting a symbol stored in a generic font format as an arrangement of pixel locations by offsetting the arrangement of pixel locations at a predetermined slope to create a staircase edge, and inserting additional pixels at predetermined locations by a predetermined transformation of the generic font format to conceal the staircase. The insertion of the staircase concealing pixels is automatic in that it is performed by the predetermined transformation. Thus, the inventive method eliminates complex pixel positioning programming that requires an analysis of the slanted pattern and a decisional process for recognizing whether a corrective pixel should be inserted at portions of the pattern. The predetermined transformation also does not substantially decrease the speed of the printing process. In addition, the inventive method does not require the storage of additional pixel information relating to the symbol. Thus, the inventive process decreases the cost of a high quality printer by not consuming more storage than necessary for storing the symbol in the generic form.